Preparation of color former dispersions



y 3 1957 P. w. VITTUM ET AL I 2,801,170

PREPARATION OF COLOR 'FORMER DISPER IONS Filed Dec. 20, 1954 COUPLER 4-LOW BOILING COUPLER SOLVENT I DISPERSION 0F COUPLER LOW BOILING SOLVENTIN $ELAT|N HIGH BOILING CRYSTALLOIDAL COUPLER SOLVENT ms znszn m DRYINGsauna DISPERSION 'OF COUPLER IN GELA'I'IN GELATINO' SILVER HALIOE EMULSION GELATINO'SILVER mun: EMULSION CONTAINING DISPERSION 0F COUPLER mmen BOILING CRYSTALLOIDAL COUPLER SOLVENT.

Paul WViitum Donald B. Julian ENTORS' W 7MZ ATTOR NEYJ United StatesPatento PREPARATION OF COLOR FORMER DISPERSIONS Paul W. Vittum andDonald B. Julian, Rochester, N. Y., assiguors to Eastman Kodak Company,Rochester, N. Y., a corporation of New Jersey Application December 20,1954, Serial No. 476,539

4Claims. (Cl. 96-97) This invention relates to color photography andparticularly to a method for incorporating couplers in silver halideemulsion layers.

In preparing dispersions of color-forming compounds in silver halideemulsions it is customary to dissolve the color former or coupler in asuitable'high boiling solvent, disperse this solution in aqueous gelatinand mix the resulting dispersion with the sensitive silver halideemulsion before coating. Ratios of coupler to solvent of about 1 to 2 or1 to 3 are usually employed (see examples of Jelley and Vittum U. S.Patent 2,322,027), although with some couplers a ratio of 1 to 1 can beused successfully. The true solubility of the couplers in the couplersolvents is, however, considerably lower than is indicated by the aboveratios and in many cases does not exceed one part of coupler in tenparts of coupler solvent. The dispersed phase inmost color formerdispersions incorporated in emulsion layers is, therefore, usually ahighly. supersaturated solution.

Even in the coupler-to-solvent ratios usually employed a large amount ofinert solvent is introduced into the emulsion and this isdisadvantageous because the inert material has no photographic functionand because it tends to decrease the physical hardness of the emulsionlayer.

In order. to reduce to a minimum the amount of the inert ingredients inthe emulsion layer and to improve the physical hardness of the coatings,it would be desirable to use smaller quantities of coupler solvent thanthose corresponding to the above ratios. To this end, etforts have beenmade to prepare coupler dispersions using smaller ratios of couplersolvent, representing, for example, ratios of coupler to solventof 1 toA: or 1 to A. Such low ratio dispersions have been successfully preparedin some cases using auxiliary solvents which are removed during thecourse of preparing. the dispersion. The same technique has been appliedto the preparation of coupler dispersions containing substantially nocoupler solvent.

With some couplers, recrystallization occurs with these low ratiodispersions. Crystal-free dispersions containing no coupler solvent canbe obtained but these dispersions nearly always yield less dye uponcolor develop ment, unless the developing solution contains an organicsolvent such as benzyl alcohol and hence, have only a limited usefulnesswhere normal color processing is required.

We have now found that it is possible to prepare dispersions ofcolor-forming couplers in gelatin emulsions, the dispersions having alow ratio of coupler to coupler solvent and showing a minimum of couplercrystallization. Our method consists in making two separate dispersions:

- (1) a solvent-free dispersion of the coupler, and (2) a dispersion ofthe high boiling coupler solvent alone. The two dispersions are thenadded in proper proportions to a gelatino-silver halide emulsion andmixed prior to coating.

The accompanying drawing is a flow sheet illustrating the stepsin ourprocess.

When proceeding in this way we believe that a rapid interaction occursbetween the two dispersions on mixing sothat, in efi'e'cL-the new methodprovides a means of avoiding the necessity for maintaining thesupersaturation of the coupler-coupler solvent system throughout the.process of removing the auxiliary solvent in which the coupler isoriginally dissolved.

Couplers which may beused according to our inventionare disclosed inJelley and Vittum U. S. Patent 2,322,027, Loria, Weissberger and VittumU. S. Patent 2,600,788 and elsewhere.

High boiling coupler solvents which are used according to our inventionto form the second dispersion mentioned above are organic crystalloidalmaterials which are substantially water-insoluble, have low molecularweight, have a boiling point'above about C. and have a high solventaction for the color-forming compound and for the dyesv formed from itand are permeable to photographic developer oxidation products in thelayer in whichthey are incorporated. Such materials includedi-n-butylphthalate and other compounds disclosed on pages 2 and 3 ofIelley and Vittum U. S. Patent 2,322,027.

Low boiling organic solvents in which the color-forming compound isfirst dissolved and which is removed to form the substantially dry orsolvent-free dispersion of coupler'in gelatin prior to mixing thedispersion of coupler with the dispersion of high boiling couplersolvent, include nitromethane, nitroethane, methyl, ethyl, propyl andbutyl acetates .and ethyl and butyl formate.

Our process is further illustrated by the flow sheet diagram in theaccompanying drawing. As shown therein,.to'a solution of coupler inlow-boiling organic coupler solvent there is added a gelatin solutionand a dispersion of the coupler and low-boiling solvent formed in thegelatin. This. dispersion is dried to remove the lowboiling solvent,leaving a dispersion of the coupler in gelatin.

A separate dispersion of high-boiling crystalloidalcoupler solvent ismade in gelatin and this dispersion and the dried dispersion of thecoupler in gelatin are added to a gelatino-silver halide emulsion.Mixing these together results in a gelatino silver halide emulsioncontaining a dispersion of coupler in high-boiling crystalloidal couplersolvent.

Our invention will now be illustrated by the following examples:

EXAMPLE I A. Preparation of solvent-free coupler dispersion V T-wogramsof the coupler 1-(2,4,6'-trichlorophenyl)- 3 [3" -'(2",4" ditent.amylphenoxyacetamido)- benzamido] .-5-pyrazolone and 8 cc. of ethylacetate were heated until the coupler was completely dissolved. To thecoupler solution there was added with stirring a mixture of 70.8 cc. of10% gelatin solution and 8 cc. of a 5% solution of Alkanol B. Themixture was passed through a colloid mill 4 times and then chilled to 40F. to gel. The gel dispersion was then shredded, spread out on astainless steel screen and dried at 72 F. and 50% relative humidity.

B. Preparation of high boiling coupler solvent dispersion 'I hree cc. ofdi-n-butylphthalate were added with stirring to a warm mixture of 35.5cc. of 10% gelatin solution and 4 cc. of a 5% oslution of Alkanol B. Themixture was passed through a colloid mill 4 times and filtered througha. silk screen to remove air bubbles.

C. Preparation of coating mixture 1.9 grams of the dried couplerdispersion A was added to a mixture of 25.2 cc. of water and 1.2 cc. ofsaponin solution. The mixture was allowed to soak for about 20 minutesand then the mixture was heated in a water bath at 40 C. 2.8 cc. of thecoupler solvent dispersion B were then added and the mixture of the twodispersions was finally added to cc. of a gelatino-silverhalide'emulsion.

The final emulsion was coated and dried in the usual way and uponexposure and development in the following solution was found to producea satisfactory magenta dye density. t

I Grams p-Aminodiethylphenylenediaminesulfate 2 Sodium sulfite,anhydrous 5 Sodium carbonate, anhydrous Potassium bromide 2 Water to 1liter.

Other primary aromatic amino developing agents may, of course, be used.EXAMPLE II A. Preparation of a solvent-free coupler dispersion Two gramsof the coupler2-[u-diamylphenoxybutyrylamino]-4,6-dichloro-5-methylphenol wasdissolved in 8.0 ml. of ethyl acetate. To this solution were added 8.0cc. of Alkanol B (5%) and 70.8 cc. of 10% gelatin solution. A dispersionwas then made by passing this mixture through a colloid mill 4 times.After the dispersion had gelled, it was shredded and washed in water (40F.) for 24 hours to remove the ethyl acetate. It was dried by spreadingthe shredded material on stainless steel screens.

B. Preparation of coupler solvent dispersion Three cc. of tri-o-cresylphosphate and 6.0 cc. of ethyl acetate were warmed and added to asolution of 35.4 cc. of 10% gelatin solution and 4.0 cc. of Alkanol B(5%). This mixture was passed through a colloid mill 4 times. The ethylacetate was removed by shredding the dispersion and washing in water at40 F. for 24 hours. The dispersion was then dried on stainless steelscreens at room temperature. 3.27 grams of this dispersion was added to19.2 cc. of water and 2.0 cc. of Alkanol B (5%). This mixture wasallowed to stand 20 minutes, at which tim it was warmed to 40 C. i

C. Preparation of the coating mixture EXAMPLE III A. Preparation of asolvent-free coupler dispersion Two grams ofN(4-benzoylacetaminobenzenesulfonyl)- N-(' -phenylpropyl)-p-toluidinewas dissolved in 8.000. of methylisobutylcarbinol. 8.0 cc. of Alkanol B(5%) 4 and 70.8 cc. of 10% gelatin solution were added to this solution.This mixture was then passed through a colloid mill four times. Theresulting dispersion was chilled, shredded and washed with water toremove the coupler solvent.

B. Preparation of the coupler solvent dispersion A solution of 35.4 cc.of 10% gelatin solution and 4.0 cc. of Alkanol B (5%) was added withstirring to 3.0 cc. of ethyl sebacate. A dispersion was then made bypassing this mixture through a colloid mill four times.

C. Preparation of the coating mixture 1.9 grams of the dried couplerdispersion A was soaked in a solution of 23.0 cc. of Water, 2.0 cc. ofAlkanol B (5% and 1.2 cc. of saponin (5%) for about 20 minutes. Thismixture was then warmed to 40 C. at which time 2.8 cc. of the couplersolvent dispersion B and 10.0 cc. of a silver halide emulsion wereadded.

The final emulsion was coated, dried, exposed and developed as inExample I and was found to produce a satisfactory yellow dye density.

It will be understood that our invention is to be taken as limited onlyby the scope of the appended claims.

We claim:

1. The method of incorporating a color former in a gelatino-silverhalide emulsion which comprises mixing a color-forming compound capableof reacting with a primary aromatic amino developing agent onphotographic development, with a low boiling water-insoluble organicsolvent for the color-forming compound said low-boiling solvent having aboiling point below C., dispersing the solution of color-formingcompound and low boiling organic solvent in gelatin, drying saiddispersion to remove substantially all organic solvent, separatelydispersing in gelatin a substantially water-insoluble, 'low molecularweight, organic crystalloidal-material having a boiling point aboveabout C., said organic crystalloidal material having a high solventaction for the color-forming compound and for dyes formed therefrom, andbeing permeable to photographic developer oxidation products, and thenmixing said dispersion of color-forming compound and said dispersion oforganic crystalloidal material, with a gelatino-silver halide emulsionto form a dispersion in the emulsion of liquid particles of'thecolorforming compound and the organic crystalloidal material.

2. The method of claim.1 in which the low boiling organic solvent isethyl acetate.

3. The method of claim 1 in which the organic crystalloidal material isdi-n-butylphthalate.

4. The method of claim l in which the low boiling organic solvent isethyl acetate and the organic crystalloidal material isdi-n-butylphthalate.

References Cited in the file of this patent UNITED STATES PATENTS Jelleyet a1. June 15, 1943 Jelley etal Aug. 9, 1949

1. THE METHOD OF INCORPORATING A COLOR FORMER IN A GELATINO-SILVER HALIDE EMULSION WHICH COMPRISES MIXING A COLOR-FORMING COMPOUND CAPABLE OF REACTING WITH A PRIMARY AROMATIC AMINO DEVELOPING AGENT ON PHOTOGRAPHIC DEVELOPMENT, WITH A LOW BOILING WATER-INSOLUBLE ORGANIC SOLVENT FOR THE COLOR-FORMING COMPOUND SAID LOW-BOILING SOLVENT HAVING A BOILING POINT BELOW 125* C., DISPERSING THE SOLUTION OF COLOR-FORMING COMPOUND AND LOW BOILING ORGANIC SOLVENT IN GELATIN, DRYING SAID DISPERSION TO REMOVE SUBSTANTIALLY ALL ORGANIC SOLVENT, SEPARATELY DISPERSING IN GELATIN A SUBSTANTIALLY WATER-INSOLUBLE, LOW MOLECULAR WEIGHT, ORGANIC CRYSTALLOIDAL MATERIAL HAVING A BOILING POINT ABOVE 175* C., SAID ORGANIC CRYSTALLOIDAL MATERIAL HAVING A HIGH SOLVENT ACTION FOR THE COLOR-FORMING COMPOUND AND FOR DYES FORMED THEREFROM, AND BEING PERMEABLE TO PHOTOGRAPHIC DEVELOPER OXIDATION PRODUCTS, AND THEN MIXING SAID DISPERSION OF COLOR-FORMING COMPOUND AND SAID DISPERSION OF ORGANIC CRYSTALLOIDAL MATERAIL, WITH A GELATINO-SILVER HALIDE EMULSION TO FORM A DISPERSION IN THE EMULSION OF LIQUID PARTICLES OF THE COLORFORMING COMPOUND AND THE ORGANIC CRYSTALLOIDAL MATERIAL. 